Introduction

Keratins are part of a large group of proteins known as intermediate filaments, which, together with actin filaments and microtubules, form the cell cytoskeleton. Keratins are widely expressed in the cytoplasm of epithelial cells, to which they confer mechanical resilience. Keratins are expressed in a tissue-specific manner and, accordingly, often demarcate pathways of embryonic development and cell differentiation. For example, keratins 8 and 18 are the only keratins detectable in preimplantation blastocyst; in the epidermis, keratins 5 and 14 are expressed in proliferating basal cells, whereas keratins 1 and 10 are the major keratins produced in more differentiated suprabasal cells.

and sequencing of various keratin genes are given in Table 1. An exhaustive list of keratin mutations can be obtained at http://www.interfil.org.

Keratins can be classified according to their isoelectric point and amino acid sequence (e.g., basic or type I, and acidic or type II), their major site of expression (e.g., epithelial keratins and hair keratins), or, their cysteine content (e.g., hard and soft keratins).

As for all other intermediate filaments, keratins are organized into two nonhelical end domains of varying sequence, flanking a central a-helical rod segment (Fig. 1). The sequences found at both ends of the rod segment are remarkably conserved across species and keratin types. They are known as the helix initiation motif (HIM) and the helix termination motif (HTM).[1]

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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